1. Field of the Invention
The present invention relates to an actuation device for a laser diode, a laser projection system and a method for speckle reduction in a laser diode.
2. Description of the Related Art
Laser projection systems use semiconductor lasers, so-called laser diodes, to project images, graphics or videos onto a projection surface. For this purpose, an appropriately modulated data signal may be applied to the laser diodes for converting the image, graphic or video data into mechanical movements of the laser projection system.
Laser diodes generate structured patterns of different brightness in a viewer's eye when coherent light impinges on an optically rough surface, when it is reflected or scattered from there and the wave fronts reflected into different directions interfere with one another. This phenomenon is also known as “speckle.” Speckle patterns adversely affect the optical impression of the projected image data, so that it is generally desirable to suppress or reduce the appearance of speckles when using laser diodes.
U.S. Pat. No. 6,600,590 B2 describes a laser projection system having a semiconductor laser, which is operated by a high frequency signal in a multi-mode operation to reduce speckles. Via a photo diode, the power of the light emitted by the semiconductor laser is detected and a constant component of the high-frequency signal of the semiconductor laser is regulated as a function of the detected power to keep the emissivity of the semiconductor laser constant.
There exists a need to regulate the speckle suppression in laser projection systems, in particular in systems having laser diodes.